High-energy phosphate compounds of rat diaphragm and skeletal muscle fibers

¹ Department of Biochemistry, University of Oregon Medical School, Portland, Oregon

The metabolism of high-energy phosphates in a muscle fiber preparation and diaphragm has been investigated. During dissection the creatine phosphate (CrP) level of fibers decreased but was reconstituted during soaking to 61% of the in situ value and remained uncharged during incubation. Dissection and soaking did not affect the adenosinetriphosphate + adenosinediphosphate (ATP + ADP) levels but incubation caused small decreases. Similar decreases in CrP and ATP levels of diaphragm occurred during incubation. The decreases in the ATP levels in fibers and diaphragm correlated with decreases in adenine absorption. A concomitant shift occurred in the absorption peak of fiber media toward the absorption maximum of hypoxanthine. In contrast, the curves for diaphragm media showed a progressive shift toward the absorption maximum for uric acid. Uricase analyses demonstrated uric acid in diaphragm media. The mesothelial covering of the diaphragm was shown to have a separate and distinct metabolism which converts hypoxanthine to uric acid. Soaking the fibers in iced buffer instead of buffer at room temperature decreased the CrP levels after incubation, ATP values were unaffected.